1. Field of the Invention
The present invention relates to an electrical junction box disposed in and fixed to a crushable zone of a vehicle.
2. Description of the Related Art
In FIG. 5, the shown electrical junction box 1, as described in Japanese Patent Application Laid-Open Publication No. 2005-119331, includes one mounting foot 3 that has a breakage-inducing portion 2 and two mounting feet 4 that do not have a breakage-inducing portion 2. Thus, the electrical junction box 1 is fixed to and inside of an engine compartment 5 via three mounting feet 3 and 4 in two types with/without the breakage-inducing portion.
The illustrated electrical junction box 1 is a relatively large component that has an elongated shape, which is fixed inside of the engine compartment 5 with its longitudinal direction usually in parallel with a front-back direction of the engine compartment 5 (which accordingly corresponds to a front-back direction of a vehicle). Two mounting feet 4 that do not have the breakage-inducing portion 2 are forwardly positioned, while one mounting foot 3 that has the breakage-inducing portion 2 is rearward positioned. Each of the mounting feet 3, 4 is fastened and fixed via a fastening bolt (not shown) provided in the engine compartment 5 and a nut (not shown) adapted to be screwed into the fastening bolt.
When an impact force when in a vehicle collision acts intensively upon the breakage-inducing portion 2 of the rearward-positioned mounting foot 3, the breakage-inducing portion 2 induces breakage (or fracture) of the mounting foot 3. The breakage-inducing portion 2 is a portion that generates breakage and separation of the mounting foot 3. Specifically, the mounting foot 3 has a shape of a relatively larger hole. The breakage-inducing portion 2 is provided at a basal portion of the mounting foot 3 (i.e., closer to the box body 6 than a portion through which the fastening bolt is passed) such that it resides at a region deviated with reference to a fixation central axis L1 of the mounting foot 3.
In addition, as shown in FIGS. 5A, 5B, central axes L2, L3 of the two mounting feet 4 are not in agreement with the fixation central axis L1 of the mounting foot 3. The fixation central axes L1 and L2 are parallel to a direction in which the impact force when in the vehicle collision is exerted.
The mounting foot 3 needs to include a breakage-inducing portion 2 in a shape of a hole, the mounting foot has to possess sufficient mechanical strength (i.e., such a strength that allow the mounting foot 3 to endure fastening by the fastening bolt and nut). In view of this, some of the ribs of the mounting foot 3 (i.e., a ring-shaped rib through which the fastening bolt is passed) is relatively thick-walled for reinforcement of the mechanical strength of the mounting foot 3.
In the above-described configuration and structure, when the engine compartment 5 collapses in the event of the vehicle collision (here, collapse occurs from a front side to a rear side of the engine compartment 5), a front wall 7 of the box body 6 of the electrical junction box 1 is pressed by a front mask 8, so that a force acts upon the box body 6 that causes the box body 6 to be displaced rearward. At this point, an impact force at the time of the vehicle collision acts upon the rearward-positioned mounting foot 3. The breakage-inducing portion 2, due to topological relation among the fixation central axes L1, L2, L3, a crack is generated with a portion of an edge of the hole at which main stress resides being the origin of the breakage. When the crack becomes larger, the mounting foot 3 is brought into breakage at its basal portion.
After the mounting foot 3 has been broken at the basal portion thereof, the electrical junction box 1 in its longitudinally-fixed state is displaced and laterally positioned, so that the electrical junction box 1 is found in an empty space provided at a rear side of the engine 9 in the engine compartment 5.
The electrical junction box 1 disclosed in the above patent literature is aimed at escaping the box body 6 in a prescribed direction when in the vehicle collision so that a property of crushability of the vehicle is not degraded. It is also contemplated in the conventional electrical junction box 1 that the box body 6 itself is protected against damage.